I am 6" and 180lbs. I ordered the Medium and it fits perfectly. I love this jacket. The vents work really well. On hot days, I open all the vents and riding is a pleasure. As other reviewers noted, it does "balloon" up when going over 65. One gets used to this over time though, but its a bit annoying at first.

I live in Santa Barbara, so the mornings are misty and often wet, but the afternoons are stunning. Opening the vents in the afternoon keeps me cool and closing them for the morning commute keeps me nice and warm. I have also ridden briefly (15mins) in the rain with this jacket and was kept nice a dry.

This is really a great jacket. The adjustability in the arms and waist ensures a perfect fit.